<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="myjQuery.js"></script>
</head>
<body>
<li>aaa</li>
<li>bbb</li>
<li>ccc</li>
<li>ddd</li>
<script>


$('li').css('color','red').addClass('nav').css('fontSize','2em');
</script>
</body>
</html>